Process of improving the magnetic qualities of iron-silicon-aluminium alloys.



UNITED STATES PATENT OFFICE.

ROBERT ABBOTT HADFIELD, OF SHEFFIELD, ENGLAND.

PROCESS OF IMPROVING THE MAGNETIC QUALITIES 0F IRON-SILICON-ALUMINIUMALLOYS.

Specification of Letters Patent.

Patented Nov. 20, 1906.

Application filed August 21, 1906. Serial No. 831,421.

To all whom it may concern:

' Be it. known that I, ROBERT ABBOTT HAD- FIELD, a subject of theofEGrelat griitlain,

, ng an ave silicon in such .proportion as to reduce the total magneticand electric losses in the mixture' (when such alloy is used forballast-coils, transformerlates, or like electric a paratus) to whicalloy aluminium is added in order to improve the solidity andhomogeneity thereof when in cast or molded condition. .In order toeffect the best reduction of the said magnetic and electric losses, 2.heat'treatment of said alloy is necessary.

Mypresent invention is a process of heat treatment applied to theaforesaid iron-silicon-aluminium alloy for the purpose stated. In carrmy invention into effect I first prepare an al oy of iron and silicon inmolten state and add aluminium or other powerful deoxidizer, cast themass into ingots, and convert the ingots into desired shapes andthicknesses by ap ropriate means. An example of such an ailloy maycontain iron and silicon in proportion of from one to five per cent. andaluminium in proportion less than one per cent. as set forth myaforesaid application. 'I' then heat said alloy to a temerature above acritical point (hereinafter efined) and then cool said alloy slowly.When said alloy is subjected to progressive temperature variations(below fusion) from 600 centigrade upward, it undergoes at a certaintemperature point an ap arent molecular change, and on further ateration of at whlch temperature another point ensues The term anothermolecular change occurs.

' critical point herein used means the oint of higher temperature of thetwo a ove noted and corresponds and approximates to the 900-cent igradepoint in the case of pure iron, which is the lower limit of itsso-called gamma state. This gamma state is definitely shown, forexamdple, in ordinary carbon-steels when heate A diagram accuratelyillustrating this oint is given by Messrs. Arnold and McW liarn in theirpaper on the thermal transformations of carbonsteels published in theJournal of the Iron and Steel Institute, 1905, Vol. 2. Diagram 2 in thispaper shows the critical point for a certain carbon-steel at about 870centigrade. In practice I have subjected my said alloy to a temperatureof about 1,050 centigrade and then cooled the same slowly at theapproximate rate of 10 centigrade per hour.

The alloy should be low in carbon and manganese.say carbon under about.12 per cent. and manganese under about .12 per cent. For certainurposes, if desired, the material as cast may he used, being suitablytreated in the same manner as the forged or rolled material. I

I clai1n v 1,. The process of increasing the magnetic permeability andelectric resistance and reducing the hysteresis action of aniron-silicon-aluminium alloy, low in carbon and manganese, whichconsists in heating said alloy to a temperature above its criticalpoint, and then cooling.

2. The process of increasing the magnetic permeability and electricresistance and reducing the hysteresis action and also of solidifyingthe structure of an iron-silicon alloy, low 1n carbon and manganese,which consists in melting iron and silicon, adding aluminium, castinginto ingot form, converting the ingot into desired sha es by appropriatemeans, then heating sai alloy to a temperature above the critical pointof said alloy and finally cooling.

In testimony whereof I have signed my name hereto in the resence of twowitnesses.

ROBERT BOTT HADFIELD.

Witnesses:

.WILLIAM Cnoss,

WILLIAM CRAWLEY;

